BBC Films is also co-financing and its head Christine Langan exec produces with Blavatnik.

Story, which is being adapted for the big screen by Jeffrey Hatcher (“The Duchess”), is set in 1947 and follows a long-retired Holmes who lives in a sleepy village outside of London with his housekeeper and her amateur-sleuthing son.

With his legendary mental powers on the wane and minus his sidekick Watson, Holmes becomes haunted by an unsolved case from 50 years ago where he remembers only fragments: a confrontation with an angry husband and a secret bond with his beautiful but unstable wife.

Pic sees Condon and McKellen (who plays Holmes) work together for the first time since 1998’s “Gods and Monsters.”

Glen Basner’s FilmNation Entertainment is handling international sales for the pic.

Condon is repped by WME, Anonymous Content, Wayne Alexander and Robert Nau.

McKellen is repped by Chris Andrews at CAA and Paul Lyon-Maris at Independent Talent Group.

Condon is in Toronto with his latest pic “The Fifth Estate,” which chronicles the rise and fall of Wikileaks and its founder Julian Assange.